Quantifying head impact biomechanical differences between commonly employed cleaning levels: a critical research interpretation consideration.

INTRODUCTION: Wearable accelerometry devices quantify on-field frequency and severity of head impacts to further improve sport safety. Commonly employed post-data collection cleaning techniques may affect these outcomes. OBJECTIVE: Our purpose was to compare game impact rates and magnitudes between three different cleaning levels (Level-1: impacts recorded within start and end times, Level-2: impacts during pauses/breaks removed, Level-3: video verified) for male youth tackle football. METHODS: Participants (n = 23, age = 10.9 ± 0.3 yrs, height = 150.0 ± 8.3 cm, mass = 41.6 ± 8.4 kg) wore Triax SIM-G sensors throughout Fall 2019. Impact rates, ratios (IRRs), and 95% confidence intervals (95%CI) were used to compare levels. Random-effects general linear models were used to compare peak linear acceleration (PLA;g) and angular velocity (PAV;rads/s). RESULTS: Level-1 resulted in higher impact rates (4.57; 95%CI = 4.14-5.05) compared to Level-2 (3.09; 95%CI = 2.80-3.42; IRR = 1.48; 95%CI = 1.34-1.63) and Level-3 datasets (2.56; 95%CI = 2.30-2.85; IRR = 1.78; 95%CI = 1.60-1.98). Level-2 had higher impact rates compared to Level-3 (1.21; 95%CI = 1.08-1.35). Level-1 resulted in higher PAV than Level-2 and Level-3 (p < 0.001) datasets. PLA did not differ across datasets (p = 0.296). CONCLUSIONS: Head impact data should be filtered of pauses/breaks, and does not substantially differ outcome estimates compared to time-intensive video verification.

Jump Height and Hip Power Decrease During Cognitive Loading Regardless of Sex: Implications for Sport Performance Metrics.

ABSTRACT: Shumski, EJ, Lempke, LB, Johnson, RS, Oh, J, Schmidt, JD, and Lynall, RC. Jump height and hip power decrease during cognitive loading regardless of sex: implications for sport performance metrics. J Strength Cond Res 37(4): 793-798, 2023-Sex and cognitive loading separately influence jumping performance. However, it is unknown how cognitive loading influences jump performance and how sex and cognitive loading interact. The purpose of our study was to determine if an interaction existed between sex and cognitive loading for the dependent variables jump height, ground contact time, reactive strength index, vertical stiffness, impulse, and lower extremity joint power during a double limb drop vertical jump. Twenty-one male (23.2 ± 2.5 years, 180.8 ± 8.4 cm, 80.4 ± 10.2 kg) and 20 female (21.7 ± 1.0 years, 163.7 ± 8.2 cm, 61.2 ± 9.4 kg) physically active individuals participated. Subjects jumped from a 30 cm box placed 50% of their height away from 2 force plates under single-task and dual-task (serial 6s or 7s) conditions. Separate 2 × 2 analyses of variance were used for all dependent variables (α = 0.05) with Bonferroni post hoc mean differences and 95% confidence intervals (CIs). There were no significant interactions for any outcomes ( p ≥ 0.190). Condition main effects demonstrated subjects jumped significantly higher (1.84 cm, 95% CI = 0.68-3.01, d = 0.26, p = 0.003) and with greater hip power (0.29 Watts·BW -1 ·HT -1 , 95% CI = 0.04-0.54, d = 0.21, p = 0.025) during single task compared with dual task. Sex main effects revealed males jumped higher (9.88 cm, 95% CI = 7.00-12.77, d = 2.17, p < 0.001), with greater reactive strength index (0.29, 95% CI = 0.17-0.41, d = 1.52, p < 0.001), greater ankle power (3.70 Watts·BW -1 ·HT -1 , 95% CI = 2.26-5.13, d = 1.64, p < 0.001), and greater knee power (5.00 Watts·BW -1 ·HT -1 , 95% CI = 3.25-6.75, d = 1.82, p < 0.001) compared with females. Jump performance is influenced by sex and dual-task conditions but not their interaction. To optimize jumping performance, testing should be completed without distractions (single task) to decrease cognitive loading.

Concussion Characteristics and Early Postinjury Outcomes Between College Students and Intercollegiate Athletes.

OBJECTIVE: To describe concussion characteristics among general college students and compare postinjury outcomes to intercollegiate student athletes. DESIGN: Retrospective cohort. SETTING: Large university in the Southeast region of the United States. PARTICIPANTS: A total of 179 (N=179) college students' (female=120; 67.0%; 23.9±3.9 years) and 49 athletes' (female=28, 57.1%;19.3±1.3 years) medical records were examined. Participants self-reported injury mechanism, health history information, and completed clinical assessments acutely (<7 days postinjury). MAIN OUTCOME MEASURES: Descriptive statistics were calculated for each group. Concussion outcomes between students with and without certain health history diagnoses were assessed using separate t tests. We conducted univariate regression analyses to determine if sex, age, and time from concussion to first clinical assessment were significant predictors of clinical outcomes. Statistically significant variables were included as covariates in a series of 1-way analyses of covariance to identify differences in balance, symptom severity, total symptom presence, and neurocognitive domain performance between students and athletes. Fisher exact tests were used to compare health history information between groups (α<0.05). RESULTS: Among students, 24% reported sustaining a concussion while participating in recreational sports, and 27% of impacts occurred to the back of the head. Students had higher proportions of headache, migraine, anxiety, and depression (P<.05). Students reported greater total symptom presence (P=.006) and performed worse on the computerized neurocognitive test domain score for complex attention (P=.015) relative to athletes. CONCLUSIONS: These findings highlight the need for better access to medical care for non- National Collegiate Athletic Association sanctioned athletes because of a large proportion of concussions in the student sample being sustained during sports participation. Identifying common injury mechanisms can provide clinicians with powerful information to improve evaluation and treatment models.

Test-Retest Reliability of a Functional Reaction Time Assessment Battery.

CONTEXT: Reaction time is commonly assessed postconcussion through a computerized neurocognitive battery. Although this measure is sensitive to postconcussion deficits, it is not clear if computerized reaction time reflects the dynamic reaction time necessary to compete effectively and safely during sporting activities. Functional reaction time assessments may be useful postconcussion, but reliability must be determined before clinical implementation. OBJECTIVE: To determine the test-retest reliability of a functional reaction time assessment battery and to determine if reaction time improved between sessions. DESIGN: Cohort. SETTING: Laboratory. PARTICIPANTS: Forty-one participants (21 men and 20 women) completed 2 time points. Participants, on average, were 22.5 (2.1) years old, 72.5 (11.9) cm tall, had a mass of 71.0 (13.7) kg, and were mostly right leg and hand dominant (92.7%). INTERVENTIONS: Participants completed 2 clinical reaction time tests (computerized Stroop and drop stick) and 5 functional reaction time tests (gait, jump landing, single-leg hop, anticipated cut, and unanticipated cut) across 2 sessions. Drop stick and functional reaction time assessments were performed in single (motor task only) and dual task (motor task with cognitive task). MAIN OUTCOME MEASURES: Reaction time (in seconds) was calculated during all assessments. Test-retest reliability was determined using 2-way mixed-effects intraclass correlation coefficients (3, k). Paired samples t tests compared mean reaction time between sessions. RESULTS: Test-retest reliability was moderate to excellent for all reaction time outcomes (intraclass correlation coefficients [3, k] range = .766-.925). Several statistically significant between-session mean differences were observed, but effect sizes were negligible to small (d range = 0.05-0.44). CONCLUSIONS: The functional reaction time assessment battery displayed similar reliability to the standard computerized reaction time assessment battery and may provide important postinjury information, but more research is needed to determine clinical utility.

Single- Versus Dual-Task Functional Movement Paradigms: A Biomechanical Analysis.

CONTEXT: Laboratory-based movement assessments are commonly performed without cognitive stimuli (ie, single-task) despite the simultaneous cognitive processing and movement (ie, dual task) demands required during sport. Cognitive loading may critically alter human movement and be an important consideration for truly assessing functional movement and understanding injury risk in the laboratory, but limited investigations exist. OBJECTIVE: To comprehensively examine and compare kinematics and kinetics between single- and dual-task functional movement among healthy participants while controlling for sex. DESIGN: Cross-sectional study. SETTING: Laboratory. Patients (or Other Participants): Forty-one healthy, physically active participants (49% female; 22.5 ± 2.1 y; 172.5 ± 11.9 cm; 71.0 ± 13.7 kg) enrolled in and completed the study. INTERVENTION(S): All participants completed the functional movement protocol under single- and dual-task (subtracting by 6s or 7s) conditions in a randomized order. Participants jumped forward from a 30-cm tall box and performed (1) maximum vertical jump landings and (2) dominant and (3) nondominant leg, single-leg 45° cuts after landing. MAIN OUTCOME MEASURES: The authors used mixed-model analysis of variances (α = .05) to compare peak hip, knee, and ankle joint angles (degrees) and moments (N·m/BW) in the sagittal and frontal planes, and peak vertical ground reaction force (N/BW) and vertical impulse (Ns/BW) between cognitive conditions and sex. RESULTS: Dual-task resulted in greater peak vertical ground reaction force compared with single-task during jump landing (mean difference = 0.06 N/BW; 95% confidence interval [CI], 0.01 to 0.12; P = .025) but less force during dominant leg cutting (mean difference = -0.08 N/BW; 95% CI, -0.14 to -0.02; P = .015). Less hip-flexion torque occurred during dual task than single task (mean difference = -0.09 N/BW; 95% CI, -0.17 to -0.02). No other outcomes were different between single and dual task (P ≥ .053). CONCLUSIONS: Slight, but potentially important, kinematic and kinetic differences were observed between single- and dual-task that may have implications for functional movement assessments and injury risk research. More research examining how various cognitive and movement tasks interact to alter functional movement among pathological populations is warranted before clinical implementation.

A Proposal for Complex Gait Evaluation Using Dual-Task Gait Termination Time.

CONTEXT: Gait termination time (GTT) has been used to predict falls in older adults but has not been explored in the sport rehabilitation setting. The incorporation of a concurrent cognitive task as a complex measure of gait in this clinical population could lead to better health-related outcomes. OBJECTIVE: To compare the effect of planned and unplanned gait termination with and without a concurrent cognitive task on reaction time (RT), gait velocity, and GTT. DESIGN: Cross-sectional. SETTING: Laboratory. PARTICIPANTS: Twenty young adults (females 60.0%, age 20.1 [0.9] y, height 169.5 [8.8] cm, mass 67.4 [10.8] kg). INTERVENTION: Participants completed 6 planned and 6 unplanned gait termination trials on an instrumented gait mat with and without a cognitive task. MAIN OUTCOME MEASURES: The authors measured RT (s), gait velocity (m/s), GTT (s), and normalized GTT (s2/m). A 2 (motor) × 2 (cognitive) repeated-measures analysis of variance (α = .05) was used; significant interaction effects were explored using Bonferroni-corrected t tests (α < .008). RESULTS: Participants walked more slowly during dual-task trials compared with single-task trials (F1,19 = 4.401, P = .050). Participants walked significantly more slowly with a cognitive task during planned (P < .001, mean difference = -0.184 m/s, 95% CI, -0.256 to -0.111) and unplanned (P = .001, mean difference = -0.111 m/s, 95% CI, -0.173 to -0.050) gait termination. Participants walked significantly more slowly (P < .001, mean difference = -0.142 m/s, 95% CI, -0.210 to -0.075) when performing the most difficult task, unplanned termination with a cognitive task, than when performing the least difficult task, planned termination with no cognitive task. We observed a cognitive task main effect such that adding a cognitive task increased RT (F1,19 = 16.375, P = .001, mean difference = -0.118 s, 95% CI, -0.178 to -0.057) and slowed normalized GTT (F1,19 = 5.655, P = .028, mean difference = -0.167 s2/m, 95% CI, -0.314 to -0.020). CONCLUSIONS: Overall, participants displayed more conservative gait strategies and slower RT, normalized GTT, and gait velocity as task difficulty increased. More investigation is needed to truly understand the clinical meaningfulness of these measures in athletic injuries.

Evaluating Multiple Domains of Health in High School Athletes With Sport-Related Concussion.

CONTEXT: Concussions are shown to hinder multiple health dimensions, including health-related quality of life (HRQOL), suggesting a need for a whole-person approach to assessment and treatment. Patient-reported outcome measures are one method to gather the patient's perspective regarding their HRQOL. OBJECTIVE: To evaluate perceived HRQOL using the Patient-Reported Outcomes Measurement Information System Pediatric-25 subscale in patients throughout concussion recovery. DESIGN: Prospective cohort, descriptive survey. SETTING: There were 9 high school athletic training facilities. PARTICIPANTS: A total of 70 patients with diagnosed concussions (51 males, 7 females, 12 unreported; age = 15.7 [0.9] y, height = 174.6 [8.4] cm, mass = 72.8 [14.8] kg, grade = 10.0 [0.9] level). INTERVENTIONS: Patient-Reported Outcomes Measurement Information System Pediatric-25 was administered at 3 days, 10 days postconcussion, and return to play (RTP). MAIN OUTCOME MEASURES: Patient-Reported Outcomes Measurement Information System Pediatric-25 subscale T scores and self-reported concussion history (yes/no). RESULTS: A total of 70 patients completed the study. For the Pediatric-25 subscales, the severity of problems associated with Physical Function Mobility, Anxiety, Depression, Fatigue, and Pain Interference were highest 3 days postconcussion, decreasing at 10 days and RTP (all p < .05). No differences were found between days 3 and 10 for Peer Relationship scores, but improvements were identified at RTP (p < .05). Pediatric-25 subscale scores at the 3 measurements were not statistically associated with concussion history (all p > .05). Ceiling and floor effects were present in all subscales throughout each timepoint, except for Physical Function Mobility (14.7%), and pain interference (11.8%) at day 3 postinjury. CONCLUSIONS: Patients who had suffered a concussion improved from day 3 through RTP on multiple health domains as demonstrated through the Pediatric-25 subscales. These findings highlight the need for health care professionals to serially monitor HRQOL and social factors that may affect the patient postconcussion as part of a multifactorial assessment. Ceiling effects in high functioning adolescent athletes were present; thus, efforts should be made to identify appropriate scales for use in managing recovery in athletic populations.

The Effect of Cognitive Rest as Part of Postconcussion Management for Adolescent Athletes: A Critically Appraised Topic.

Clinical Scenario: It is hypothesized that cognitive activity following a concussion may potentially hinder patient recovery. While the recommendation of cognitive rest is often maintained and rationalized, a causal relationship between cognitive activity and symptom duration has yet to be established. CLINICAL QUESTION: Does the implementation of cognitive rest as part of the postconcussion management plan reduce the number of days until the concussed adolescent patient is symptom free compared to a postconcussion management plan that does not incorporate cognitive rest? Summary of Key Findings: A thorough literature search returned 7 possible studies; 5 studies met the inclusion criteria and were included. Three studies indicated that increased cognitive activity is associated with longer recovery from a concussion, and, therefore, supported the use of cognitive rest. One study indicated that the recommendation for cognitive rest was not significantly associated with time to concussion symptom resolution. One study indicated that strict rest, defined as 5 days of no school, work, or physical activity; might prolong symptom duration. Clinical Bottom Line: There is moderate evidence to support the prescription of moderate cognitive rest for concussed patients. Clinicians who intend on implementing cognitive rest in their concussion protocols should be aware of inconsistencies and be open-minded to alternative treatment progressions while taking into consideration each individual patient and maintaining adequate patient-centered care principles. Strength of Recommendation: Grade B evidence exists that prescription of moderate cognitive rest for concussed patients may be beneficial as a supplement to physical rest as treatment for symptom reduction in adolescents.

Concussion Characteristics in Adults With ADHD Seen in a Specialty Concussion Clinic.

BACKGROUND: Concussions are a prevalent health concern, affecting millions of individuals in the United States yearly. Concussion symptomology overlaps with other conditions making diagnosis and management particularly challenging, particularly among individuals with ADHD. ADHD is a neurodevelopmental disorder that affects a significant portion of the adult population. OBJECTIVE: To enhance our understanding of symptom resolution and identify factors that could influence concussion care management, the purpose of the current study was to examine the recovery trajectory of adults diagnosed with both ADHD and concussion compared to the trajectory of adults who have experienced a concussion but do not have an ADHD diagnosis. METHODS: The study included a retrospective chart review of patients treated for concussion at a concussion specialty clinic. RESULTS: The findings of the study revealed no significant differences in history of concussion or recovery time between patients with and without ADHD. It was observed that patients with ADHD had a higher prevalence of anxiety, depression, and other mental health conditions. CONCLUSIONS: The findings of the current study underscore the need for additional research to guide the care of patients diagnosed with both ADHD and concussion.

Effects of shoe collar types on ankle and knee biomechanics characteristics when performing the side-step cutting task.

This study aimed to examine the effect of football shoes with different collar types on ankle and knee kinematic and kinetics features during 45° and 135° side-step cutting tasks. Fifteen healthy college football players volunteered for the study. Each participant was instructed to perform side-step cutting tasks with high, low, and no collar football shoes. The kinematic and ground reaction force data were measured using a Vicon motion capture system and a Kistler force plate, respectively. Two-way MANOVAs with repeated measures were used to examine the effect of shoe collar type and task conditions. There were no interaction effects. The high collar football shoe showed decreased ankle range of motion in the sagittal plane (p = 0.010) and peak ankle external rotation moment (p = 0.009) compared to the no collar football shoe. The high (p = 0.025) and low (p = 0.029) collar football shoes presented greater peak ankle external rotation angles than the no collar football shoe. These results imply that football shoes with high collars made of high intensity knitted fabric could be used to restrict ankle joint movement, with potential implications for decreasing the risk of ankle sprain injuries in football players.

Youth Tackle Football Head-Impact Estimation by Players and Parents: Is the Perception the Reality?

CONTEXT: With growing concerns surrounding exposure to head impacts in youth tackle football, players and parents must understand the exposure level when assenting and consenting to participate. OBJECTIVE: To determine whether youth football players and parents could estimate on-field head-impact frequency, severity, and location. DESIGN: Prospective cohort study. SETTING: Football field. PATIENTS OR OTHER PARTICIPANTS: We administered a 10-question head-impact estimation tool to parents (n = 23; mean age = 36.5 years [95% CI = 31.7, 37.3 years]) and players (n = 16 boys; mean age = 11.1 years [95% CI = 10.3, 11.8 years]). MAIN OUTCOME MEASURE(S): Player on-field head-impact exposure was captured using the Triax SIM-G system. We determined the accuracy between player and parent estimates relative to on-field head-impact exposures using κ and weighted κ values. RESULTS: Youth tackle football players and parents did not accurately estimate on-field head-impact frequency (κ range = -0.09 to 0.40), severity (κ range = -0.05 to 0.34), or location (κ range = -0.30 to 0.13). Players and parents overestimated head-impact frequency in practices but underestimated the frequency in games. Both groups overestimated head-impact severity, particularly in games. Most players and parents underestimated the number of head impacts to the top of the head, particularly during practices. CONCLUSIONS: Underestimations of head-impact frequency in games and to the top of the head suggest that informed consent processes aimed at educating players and parents should be improved. Overestimations of head-impact frequency in practices and severity may explain declining rates of youth tackle football participation.

University educators' perceptions of academic adjustments following a concussion for student-athletes and non-student-athletes.

Objective: To identify (1) university educators' perceptions of academic adjustments (AA), and (2) if teaching experience correlated with AA perceptions following concussion. Participants: Two hundred twenty educators. Methods: University educators were invited to complete a survey containing four subsections; this manuscript focuses on AA following concussion. Objective 1 was descriptive; we conducted spearman's rho correlations between years of teaching experience and AA perceptions to address objective 2. Results: Educators were moderately familiar with AA but were not confident in their knowledge about AA following concussion. Participants who provided AA following concussion most often allowed excused absences and extra time for exams/assignments. There were no significant relationships between teaching experience and perceptions of AA. Conclusions: University educators largely feel unprepared to provide or recommend AA following concussion but had favorable AA perceptions following concussion. Standardized policies or referral sites within the university system may be warranted to improve post-concussion AA.

On-field Characteristics and Head Impact Magnitude in Youth Tackle Football.

BACKGROUND: This study determined the effect of video-verified collision characteristics on head impact magnitudes in male youth tackle football. METHODS: Participants (n = 23, age = 10.9 ± 0.3 years, height = 150.0 ± 8.3 cm, mass = 41.6 ± 8.4 kg) wore Triax Sim-G sensors throughout the fall 2019 season. Ten filmed games were used to identify nine different collision characteristics: mechanism, preparedness, head direction, struck versus striking activity, stance, play type, closing distance, penalty, and quarter. Random-effects general linear models and Cohen d effect sizes were used to examine differences in log-transformed peak linear (PLA; g) and rotational (PRA; rad/s2) accelerations across characteristics. The 10 games produced 533 total video-verified impacts and 23.2 ± 7.2 impacts per athlete. RESULTS: PLA (P range: 0.107 to 0.923) and PRA (P range: 0.057 to 0.768) did not differ across characteristics. Struck players (3370 rads/s2, 95% confidence interval [CI] = 2986 to 3808) had a small effect for higher PRA compared with striking players (3037 rads/s2, 95% CI = 2713 to 3404, d = 0.251), but negligible effect for simultaneous struck-striking players (3340 rad/s2, 95% CI = 2945 to 3792, d = 0.018). Fourth quarter impacts (3490 rads/s2, 95% CI = 3083 to 3951) had a small effect for higher PRA compared with first (2945 rads/s2, 95% CI = 2596 to 3337, d = 0.404), second (3196 rads/s2, 95% CI = 2832 to 3604, d = 0.219), and third quarters (3241 rads/s2, 95% CI = 2841 to 3699, d = 0.144). CONCLUSION: Youth tackle football characteristics did not significantly affect head impact magnitudes during games. More research is needed to explore additional factors that could be modified for sport safety rather than mitigating impact mechanism.

Head Impact Biomechanics in Youth Flag Football: A Prospective Cohort Study.

BACKGROUND: Youth flag football participation has rapidly grown and is a potentially safer alternative to tackle football. However, limited research has quantitatively assessed youth flag football head impact biomechanics. PURPOSE: To describe head impact biomechanics outcomes in youth flag football and explore factors associated with head impact magnitudes. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: We monitored 52 player-seasons among 48 male flag football players (mean ± SD; age, 9.4 ± 1.1 years; height, 138.6 ± 9.5 cm; mass, 34.7 ± 9.2 kg) across 3 seasons using head impact sensors during practices and games. Sensors recorded head impact frequencies, peak linear (g) and rotational (rad/s2) acceleration, and estimated impact location. Impact rates (IRs) were calculated as 1 impact per 10 player-exposures; IR ratios (IRRs) were used to compare season, event type, and age group IRs; and 95% CIs were calculated for IRs and IRRs. Weekly and seasonal cumulative head impact frequencies and magnitudes were calculated. Mixed-model regression models examined the association between player characteristics, event type, and seasons and peak linear and rotational accelerations. RESULTS: A total of 429 head impacts from 604 exposures occurred across the study period (IR, 7.10; 95% CI, 4.81-10.50). Weekly and seasonal cumulative median head impact frequencies were 1.00 (range, 0-2.63) and 7.50 (range, 0-21.00), respectively. The most frequent estimated head impact locations were the skull base (n = 96; 22.4%), top of the head (n = 74; 17.2%), and back of the head (n = 66; 15.4%). The combined event type IRs differed among the 3 seasons (IRR range, 1.45-2.68). Games produced greater IRs (IRR, 1.24; 95% CI, 1.01-1.53) and peak linear acceleration (mean difference, 5.69g; P = .008) than did practices. Older players demonstrated greater combined event-type IRs (IRR, 1.46; 95% CI, 1.12-1.90) and increased head impact magnitudes than did younger players, with every 1-year age increase associated with a 3.78g and 602.81-rad/s2 increase in peak linear and rotational acceleration magnitude, respectively (P≤ .005). CONCLUSION: Head IRs and magnitudes varied across seasons, thus highlighting multiple season and cohort data are valuable when providing estimates. Head IRs were relatively low across seasons, while linear and rotational acceleration magnitudes were relatively high.

Clinical versus Functional Reaction Time: Implications for Postconcussion Management.

PURPOSE: This study aimed to examine the association between clinical and functional reaction time (RT) assessments with and without simultaneous cognitive tasks among healthy individuals. METHODS: Participants (n = 41, 49% female; 22.5 ± 2.1 yr; 172.5 ± 11.9 cm; 71.0 ± 13.7 kg) completed clinical (drop stick, Stroop) and functional (gait, jump landing, single-leg hop, anticipated cut, unanticipated cut) RT assessments in random order. All RT assessments, except Stroop and unanticipated cut, were completed under single- (movement only) and dual-task conditions (movement and subtracting by 6s or 7s). Drop stick involved catching a randomly dropped rod embedded in a weighted disk. Stroop assessed RT via computerized neurocognitive testing. An instrumented walkway measured gait RT when center-of-pressure moved after random stimulus. All other functional RT assessments involved participants jumping forward and performing a vertical jump (jump landing), balancing on one leg (single-leg hop), or a 45° cut in a known (anticipated cut) or unknown (unanticipated cut) direction. RT was determined when the sacrum moved following random visual stimulus. Pearson correlation coefficients and a 5 × 2 repeated-measures ANOVA compared RT assessments and cognitive conditions. RESULTS: Stroop RT outcomes did not significantly correlate with functional RT assessments (r range = -0.10 to 0.24). A significant assessment by cognitive task interaction (F4,160 = 14.01; P < 0.001) revealed faster single-task RT among all assessments compared with dual-task (mean differences, -0.11 to -0.09 s; P < 0.001), except drop stick (P = 0.195). Single-leg hop (0.58 ± 0.11 s) was significantly slower compared with jump landing (0.53 ± 0.10 s), anticipated cut (0.49 ± 0.09 s), gait (0.29 ± 0.07 s), and drop stick (0.21 ± 0.03 s; P values ≤ 0.001). Dual-task assessments were significantly slower than single-task assessments (mean difference, 0.08 s; P < 0.001). CONCLUSIONS: Clinical and functional RT assessments were not correlated with each other, suggesting that sport-like RT is not being assessed after concussion. Functional and dual-task RT assessments may add clinical value and warrant further exploration after concussion.

A Comparison of Youth Flag and Tackle Football Head Impact Biomechanics.

Our purpose was to describe the youth flag football head impact burden and make comparisons with youth tackle football. Head impact frequency and magnitude (linear acceleration [g], rotational acceleration [rad/s2]) were collected from 25 tackle and 25 flag youth football players over one season. Athlete exposure (AE) was defined as one player participating in one session. Head impact rates (IR) were calculated and impact rate ratios (IRR) were used to compare youth tackle and flag football. Random-intercept generalized logit models with odds ratios compared the probabilities of sustaining an impact with a linear acceleration of 20.00-29.99g, 30.00-39.99g, and ≥40.00g against the reference of 14.00-19.99g and an impact with a rotational acceleration of 2500.00-7499.99 rad/s2 or ≥7500.00 rad/s2 against the reference of ≤2499.99 rad/s2 between youth flag and tackle football. We observed 1908 tackle football head impacts (735 in games, 38.5%) across 624 AE and 169 flag football head impacts (101 in games, 59.8%) across 255 AE. Youth tackle football players experienced higher overall IR (3.06, 95% confidence interval [CI]: 2.61, 3.58; IRR = 4.61, 95% CI: 3.94, 5.40) compared with flag football (IR = 0.66, 95% CI: 0.57, 0.78). Youth flag football players had lower odds of sustaining impacts >20g but higher odds of sustaining impacts between 2500.00-7499.99 rad/s2 compared with youth tackle players. Our preliminary sample of youth flag football players sustained less frequent head impacts at higher rotational accelerations than tackle football players. Flag football is considered a limited-contact sport, but little is known about the true head impact burden. Our findings may be important for policymakers when debating potential changes to youth football participation.